[MITgcm-support] MPI problem on Archer (CRAY XC30)

[David Ferreira]

Hi all,
I'm having a problem running the coupled model on Archer.
The Archer support team discovered the following problem:

##########
...
---
Rank 0 [Tue Oct  7 22:44:10 2014] [c7-0c1s12n2] Fatal error in MPI_Recv: 
Invalid
tag, error stack:
MPI_Recv(192): MPI_Recv(buf=0x7fffffff8000, count=1024, MPI_INTEGER, 
src=1, tag=9862928,
  comm=0x84000004, status=0x7fffffff7df0) failed
MPI_Recv(113): Invalid tag, value is 9862928
---

The maximum allowed value for the "tag" in MPI messages on Cray XC30 systems
is 4194303, which explains the error message

MPI_Recv(113): Invalid tag, value is 9862928

The MPI standard only requires that the maximum tag value is not less than
32767 (so Cray MPI is compliant). The maximum can be larger, and can be 
found
using the MPI_Get_attr enquiry function. Your program should retrieve 
this value
and ensure that any tags it specifies are no larger.

##########

I have absolutely no clue how to tell the model to choose MPI tags which 
are below 4194303.
A bit of googling on MPI_Get_attr led me to some very obscure pages.

Any help is welcome.
Cheers,
david